This invention relates to an electrophotographic process wherein an image developed with finely divided toner particles is fixed by a flash fixation procedure.
In conventional electrophotographic processes wherein electrophotographic devices such as printers, facsimiles and copiers are utilized, images developed with finely divided toner particles are usually fixed by using an oven or heated roller. However, the finely divided toner particles used in these conventional electrophotographic processes are not suitable for a process wherein developed images are fixed by means of flash fixation. The term "flash fixation" as used herein means a fixation procedure wherein a toner image is fixed by irradiating the toner image with high energy ultraviolet or visible light to instantly elevate the temperature of the toner to a point at which the toner is molten.
Most of the conventional finely divided toner particles comprise resin binders which are based upon styrene/acrylic acid ester copolymers, as described in, for example, Japanese Laid-open Patent Applications Nos. 17,434/72, 17,435/72, 8,141/73, 16,646/73, 75,033/73, 78,936/73, 79,639/73, 90,238/73, 90,132/74, 44,836/75 and 23,941/77. If the styrene/acrylic acid ester copolymer-based toners are used in an electrophotographic process wherein the developed toner images are fixed by means of flash fixation, the styrene/acrylic acid ester copolymer tends to be degraded, namely, the main chain of the styrene/acrylic acid ester copolymer tends to be broken at the ester bond portions, thereby producing low molecular weight substances such as styrene, xylene, isopropylbenzene, butanol, isobutyl acetate, methyl methacrylate and butyl methacrylate.
Furthermore, most of the conventional finely divided toner particles contain, as a colorant, carbon and various organic dyes. Particularly, some commercially available toners contain only an organic dye as a colorant. Typical organic dyes used include, for example, heavy metal-containing acid dyes and Nigrosine base dyes. The heavy metal-containing acid dyes have a problem in that the heavy metal contained therein is toxic. The Nigrosine base dyes have a problem in that, when the developed toner images are fixed by means of flash fixation, the dyes tend to produce low molecular weight substances, such as nitrobenzene, aniline and biphenylamine, due to the decomposition of the dyes.
In other words, when the conventional finely divided toner particles are used in an electrophotographic process wherein the developed toner images are fixed by means of flash fixation, the toner particles produce gaseous, low molecular weight substances which emit an offensive odor and are detrimental to health.